Oil burner control-program type



s- 194. c1'.wAL|.|s ET AL 2,212,

OIL BURNER CONTROL-PROGRAM TYPE Filed May 5, 1937 W Cyzl T9021! Z158: I Webs ii diva/15 Patented Aug. 20, 1940 Fowler, Birmingham, Mich., assignors to General Motors Corporation, Detroit, Mich a corporation of Delaware Application May 5, 1937, Serial No. 140,824

4 Claims.

Ourinvention pertains to control apparatus and more particularly to automatic controlling means for fluid fuel burners for heating and is related to our copending application Ser. No. 1 8,-

5 688 filed April 24, 1937.

1 In the usual construction of either mechanism for burning oil or gas or, other fluid fuel, it is necessary to provide some automatic means "for controlling the periods of actuation of the burner and the regulation ofthe temperature in the space to be heated, the primary function of course being to actuate the burner as the temperature falls below a predetermined point and to cause'itito' cease operatingas the temperature rises back uptto the set point. There are however, over and above these normal variations, safety precautions which must be provided in case the burner does not operate in the usual manner ;for example, if the burner does not start to provide heat when: actuated or if there is a flame failure or current failure when the burner is operating normally, means must be provided for shutting down the whole system to prevent an explosion or destruction of a portion of the 2.3 apparatus. I

It is therefore an object of our invention to provide a simple system for so controlling a burner as to provide the necessary safety features as above pointed out. V t With this andother objects in view, the embodiments of our invention are disclosed in the following specification and claims and illustrated in the accompanying drawing, in which the figure illustrates a schematicwiringdiagram of our inventi'o'n. e v

The essential parts of our control apparatus are a roomthermostat 2, astack thermostat 4 0 ,rated-by' the combustion temperature within the furnace, an electrically heated safety switch 6, a

pair of control-"relays 8 and II], a motor !2 for projecting fuel into the combustionchaniber, an

"ignition transformer 14 anda main control trans- The systemmay be roughly dividedinto'two 'classes:-thehigh Voltage and the low voltage side. In the high voltage portion there is connected the motor l2, the ignition transformer 14, the main motor switch l8, an ignitionswitch 20; primary coil 22 of the transformer l6 and safety switch 24 whose contacts are under 'normal' c'onditions closed. These devices are con- "nected in the line in the following manner: 'from the main supply line 26 is connected a line 28 to the safety'switch 24 from which extendsa line 30to the motor switch l8. From'the motor ,former M by a line 42.

switch [8 one line 32 extends to one terminal of the motor and a second line 34 extends to the ignition switch 20. From the other terminal of .the ignition switch 20 is a line 36 extending to the transformer l4 and from the opposite side of the motor |2 a line 38 extends back to the other supply line 40 and to this line 38 is connected the opposite side of the ignition trans- The primary 22 of the main transformer is To} connected directly across the incoming line 26 and 4B. The secondary 44 of the transformer l6lsupplies energy for operating the main control apparatus and one'side of said secondary is connected by line 46 to the room thermostat 2 and from the room thermostat 2 extends a line 48 which is connected to one of the control relays 8 which is connected in series with the heating coil 50 of the warp switch 6 by line 52. From the 0p-,. posite terminal of the heating coil 50 extends a20 line 54 which is connected back to the opposite terminal of the secondary 44. It will thus be seen that when the room thermostat calls for heat the relay 8 and heating coil 50 are energized directly by the secondary and are in series.

Also extending from the opposite end of the heating coil 50 is a line 56 to which'is connected a switch 58, the opposite point of the switch being connected by line 60 to a switch 62 operated, by stack switch 4 and being normally closedwhen 30 the combustion chamber is cold and open when the combustion chamber is heated. A, line 64 extends from the stack switchto the other control relay ID, the opposite terminal of which. is connected by line 66 to switch.68, the opposite por- '35 tion of the switch being connected back to line 48 which extendsfromthe room thermostat.

Extending fr'om'theline 64 is an additional line 10 which connects to aswitch 12 the opposite terminal of which is connected by line 14 ,t0a 40 second stack switch 16 which is normally open when the combustion chamber istcold and closed when the latter is heated, said opposite te'rminal of thestack'switch 16 being connectedby line 18 to line 54. The switch 12 is adapted to be ac- "Z5 tuated by the relay l0 and may be termed the holding contacts" l The safety switch 24 is composed of one stationary terminal and one movable terminal, the latter being mounted on a pivoted arm '80 which 50 is spring bias-ed away from the stationary contact and it is held in position as shown by a bimetallic arm 82 but as will be seen when the bimetallic arm warps downwardly, as shown in the drawing, it will move out of contact with the end 55 of the arm 88 and allow the same to spring to the right opening the'safety switch. However the rod 84 actuated by the bimetallic stack element 86 is adapted to project into the path of the pivoted arm 80 and to prevent its movement in case the combustion chamber has heated so that if the thermal element moves out of the way the stack arm will act as an interlock and prevent the safety switch from opening if the burner operates normally.

The operation of my circuit will now be described. When the room thermostat 2 calls for heat it closes its contacts and the following circuit is completed to energize the relay 8 and the heating coil 58. From transformer secondary 44, line 46, room thermostat 2, line 48, relay 8, line 52, heating coil, 50, line 54, back to secondary 44. This energizes the heating coil which starts to heat the bimetallic arm 82 which will cause the latter to warp out of its stop position. At the same time the relay 8 is energized and it closes contacts 68 thereby energizing relay I" through the following circuit: Secondary 44, line 46, room thermostat 2, line 48, switch 68, line 66, relay 10, line 64, stack switch 62, closed when *com, line' 68, switch as (closed when so is cold),

line 56,line 54 back to the secondary.

It will be evident from the above that in the initial energizing circuit for the relay l there are two switches in series, namely 62, operated by the stack switch, and '58, operated by the warp switch, to insure that both of these members are in their normal cold or deenergized position before the burner may be started. If either one is open the system will not start.

Upon the energization of the relay II] the switch [8 in the main motor circuit is closed thereby energizing the motor through the following circuit: Line 26, line 28, safety switch 24, line 38, switch l8, line 32, motor l2, line 38 back to incoming line 48. At the same time the ignition transformer will be energized through the same line as far as switch I8 and from there through line 34, ignition switch 20, line 36, ignition transformer [4 to line 38 back to the incoming line. This will start the motor and ignition in operation and under normal conditions the burner will commence operation.

As the bimetallic arm 82 heats, it will warp in a downward direction as shown which will break the ignition switch 20 after a certain set time which will cut off the ignition and it will also break the contacts in switch 58 which would ordinarily break the circuit for relay l0. However when relay l0 closed it also closed switch 12 which acts as a holding circuit for the relay since bythis' time switch 16. operated by the stack has closed to complete the by-pass or holding circuit for the relay [0 and insuring heat before the holding circuit is complete. If the stack has not heated up by the time that switch :58 or switch .62 opens, the relay I0 will be deenergized. It might be, mentioned at this piont that the switch- ,es62 and 16 are of the overlapping type in one direction, namely to the left or from 62 to 16, so that switch 16 makes before switch 62 breaks. Also, if the burner does not heat when the warp switch plate 82 passes beyond the end of the spring biasarm88, the latter will fly to the right and open the safety switch if the rod 84 has not been thermally positioned into contact with the out of position allowing the safety switch 24 to open which requires a manual reset. If there is a current failure during normal operation, holding switch I2 will open deenergizing relay In which operates the motor switch and the motor will be stopped. The energizing circuit for relay I8 cannot again be closed due to the fact that switch 58 is open and therefore as the combustion chamber cools down rod 84 will again allow the safety switch 24 to open;

We claim:

1. In a system for controlling fluid fuel burners, a burner circuit, a safety switch in said ,circuit having an actuator with a heating element for opening said switch when said actuator is heated by said heating element, means operative on establishment of combustion to mechanically engage said safety switch and prevent the opening thereof, electrically operated means to control said burner circuit, a control circuit for said electrically operated means, a thermostat with said heating element in series therewith to energize said control circuit, a normally closed stack switch in said control circuit adapted to be opened in response to combustion temperature, and a normally closed timer switch inseries with said stack switch and adapted to be opened by said safety switch actuator when heated.

2. In a system for controlling fluid fuel burners, a burner circuit, a safety switch in said Circuit having an actuator with a heating element for opening said switch when said actuator is heated by said heating element, means operative on establishment of combustion to mechanically engage said safety switch and prevent the opening thereof, electrically operated means to control said burner circuit, a control circuit for said electrically operated means, a thermostat with said heating element in series therewith to energize said control circuit, a normally closedv stack switch in said control circuit adapted to be opened in response to combustion temperature, a normally closed timer switch in series with said stack switch and adapted to be opened by said safety switch actuator when heated, and a holding circuit for said electrically operated means having a second stack switch which is normally open and adapted to be closed in response to combustion temperature prior to opening of said firstmentioned stack switch.

3. In a system for controlling fiuid fuel burners, a burner circuit, an ignition circuit, a safety switch controlling said circuits having an actuator with a heating element for opening said switch when said actuator is heated by said heating element, means operative on establishment of combustion to mechanically engage said safety switch and prevent the opening thereof, electrically operated means to control said burner and ignition circuit, a control circuit for said electricallyoperated means, a thermostat with-said heating element in series therewith to energize said control circuit, a normally closed stack switch in said control circuit adapted to be opened in response to combustion temperature, a normally closed timer switch in series with said stack switch in said control circuit and a normally closed timer switch in said ignition circuit, both of said timer switches adapted to be opened by said safety switch actuator. when heated. I

4. In a system for controlling fluid fuel burners, a burner circuit, an ignition circuit, a safety switch controlling said circuits having an actuator with a heating element for opening said switch when said actuator is heated by said heating element, means operative on establishment of combustion to mechanically engage said safety switch and prevent the opening thereof, electrically operated means to control said burner and ignition circuits, a control circuit for said electrically operated means, a thermostat with said heating element in series therewith to energize said control circuit, a normally closed stack switch in said control circuit adapted to be opened in response to combustion temperature, a normally closed timer switch in series with said stack switch in said control circut, a normally closed timer switch in said ignition circuit, both of said timer switches adapted to be opened by said safety switch actuator when heated, and a holding circuit for said electrically operated means having a second stack switch which is normally open and adapted to be closed in response to combustion temperature prior to opening of said firstmentioned stack switch.

CYRIL T. WALLIS.

ROBERT E. FOWLER. 

